1. Field of the Invention
This invention concerns tank-ship construction in general, and more particularly relates to certain elements of the structure employed for supplying an inert gas to a plurality of tanks in a tank ship. Specifically, it concerns the combination of a valve located in a conduit for supplying the inert gas, along with a vent hatch located in the same conduit adjacent to the valve.
2. Description of the Prior Art
In tank ships that are designed for carrying petroleum products, it has been found (particularly in the large-sized tankers now generally being constructed) that the danger of explosive atmospheres developing in empty or partially empty cargo tanks becomes extremely great. In order to overcome this situation, one of the most universally acceptable procedures is that of introducing an inert gas to the empty tank space involved. Such introduction of inert gas involves the use of a main conduit for supplying the inert gas, along with branch conduits to individual tanks. Heretofore, such systems have relied upon the use of so-called pressurevacuum valves for avoiding excess over- or under-pressure in the tanks. However, these pressures involved are quite low, and the use of such breather valves entails expensive mounting. Also, because such low pressure safety-valve instruments are relatively delicate, they are more subject to fouling, and consequently the safety factor might be lost.
Consequently, it is an object of this invention to provide a simple yet effective combination that is particularly applicable to petroleum tank ship structures.